Tree sprouts centrally produced in nurseries are used extensively in forest planting operations. Planting trays which consist of a set of recessed cells formed out of a sheet of polymeric material, are commonly used to shelter the tree sprouts during the early stages of growth. The cells are filled with a growing substratum into which the seed is planted. The seeds grow inside the cell until the sprout is ready to be planted in the ground.
In order to minimize the risk of damaging the fragile sprouts, they are transported to the planting sight in the trays and are only retracted from the cells on the field, during the actual planting operation.
The planting operation involves forming a recess in the ground, dropping the sprout into the recess and then covering the roots with soil. The planting operation, which often takes place on accidented terrain, requires the tree planting person to carry the trays to the planting location and perform a variety of movements such as bending and twisting his trunk, kneeling and squatting.
To further complicate the situation, the tree planting person is often paid according to the amount of sprouts planted and must thus perform these movements as quickly and efficiently as possible.